Magnetically actuated photonic crystal sensor

ABSTRACT

A magnetically actuated photonic crystal sensor is disclosed. An optical fiber comprises at least one photonic crystal means coupled to a first end thereof, and a magnetic material coupled to the at least one photonic crystal means.

CROSS-REFERENCE TO RELATED APPLICATION

The present application is a divisional application of U.S. patentapplication Ser. No. 12/859,255, entitled “Magnetically ActuatedPhotonic Crystal Sensor” filed on Aug. 18, 2010, the content of which isincorporated by reference herein in its entirety.

FIELD

Embodiments of the present disclosure relate generally to sensors. Moreparticularly, embodiments of the present disclosure relate to magneticsensors.

BACKGROUND

Optical sensing systems and methods are highly desirable due to theirinherent Electromagnetic Interference (EMI) and High Intensity RadiatedField (HIRF) immunity. Optical sensing designs aimed at applicationssuch as structural health monitoring currently involve placing opticalsensors in direct contact with an environment or object to be sensed.Some sensing applications such as proximity sensing may currentlyrequire use of light emission and detection, direct physical contact, ordirect physical obstruction by optical sensing systems and methods inorder to function optimally. In at least such applications, currentoptical sensing systems and methods may generally have low reliabilityin an environment comprising obscurants, obstructions, debris, andpotential for physical deformation.

SUMMARY

A magnetically actuated photonic crystal sensor is disclosed. An opticalfiber comprises a photonic crystal coupled to a first end thereof, and amagnetic material coupled to the photonic crystal.

In a first embodiment, a magnetically actuated photonic crystal sensorcomprises an optical fiber comprising a first end. At least one photoniccrystal means is coupled to the first end, and at least one magneticmaterial is coupled to the at least one photonic crystal means.

In a second embodiment, a method for using a magnetically actuatedphotonic crystal sensor system comprises receiving a received magneticforce on a magnetic material coupled to a photonic crystal such that thephotonic crystal is actuated by the received magnetic force. The methodfurther transmits a transmitted light through an optical fiber to thephotonic crystal. The method then receives a reflected light through theoptical fiber from the photonic crystal. The method further determines adetermined difference in the reflected light from the transmitted light.

In a third embodiment, a method provides a magnetically actuatedphotonic crystal sensor. The method provides a photonic crystal andcouples the photonic crystal to a first end of an optical fiber. Themethod then couples a magnetic material to the photonic crystal.

This summary is provided to introduce a selection of concepts in asimplified form that are further described below in the detaileddescription. This summary is not intended to identify key features oressential features of the claimed subject matter, nor is it intended tobe used as an aid in determining the scope of the claimed subjectmatter.

BRIEF DESCRIPTION OF DRAWINGS

A more complete understanding of embodiments of the present disclosuremay be derived by referring to the detailed description and claims whenconsidered in conjunction with the following figures, wherein likereference numbers refer to similar elements throughout the figures. Thefigures are provided to facilitate understanding of the disclosurewithout limiting the breadth, scope, scale, or applicability of thedisclosure. The drawings are not necessarily made to scale.

FIG. 1 is an illustration of an exemplary magnetically actuated photoniccrystal sensor system according to an embodiment of the disclosure.

FIG. 2 is an illustration of an exemplary magnetically actuated photoniccrystal sensor showing a photonic crystal installed on a tip of anoptical fiber according to an embodiment of the disclosure.

FIG. 3 is an illustration of an exemplary silicon crystal base accordingto an embodiment of the disclosure.

FIG. 4 is an illustration of an exemplary photonic crystal latticecomprising a plurality of etched holes according to an embodiment of thedisclosure.

FIG. 5 is an illustration of an exemplary photonic crystal comprising aplurality of etched holes separated from a substrate to form a photoniccrystal lattice according to an embodiment of the disclosure.

FIG. 6 is an illustration of a perspective bottom view of the photoniccrystal shown in FIG. 5 according to an embodiment of the disclosure.

FIG. 7 is an illustration of an exemplary multi-layer Fabry-Perot(etalon) Interferometer formed from two photonic crystals according toan embodiment of the disclosure.

FIG. 8 is an illustration of an exemplary multi-layer Fabry-Perot(etalon) Interferometer coupled to a Micro-Electro-Mechanical System(MEMS) frame according to an embodiment of the disclosure.

FIG. 9 is an illustration of an exemplary multifunction photonic crystalsensor according to an embodiment of the disclosure.

FIG. 10 is an illustration of a result of a patterning step, adirectional etching step, a first oxide-etching step, and arelease-etching step in a process for forming a multifunctionmagnetically actuated photonic crystal sensor according to an embodimentof the disclosure.

FIG. 11 is an illustration of a result of an oxide deposition step and apolysilicon deposition step in a process for forming a multifunctionmagnetically actuated photonic crystal sensor according to an embodimentof the disclosure.

FIG. 12 is an illustration of a second oxide-etching step in a processfor forming a multifunction magnetically actuated photonic crystalsensor according to an embodiment of the disclosure.

FIG. 13 is an illustration of a silicon-etching step, a backsidesilicon-etching step, and a magnet-mounting step in a process forforming a multifunction magnetically actuated photonic crystal sensoraccording to an embodiment of the disclosure.

FIG. 14 is an illustration of a fiber-mounting step in a process forforming a multifunction magnetically actuated photonic crystal sensoraccording to an embodiment of the disclosure.

FIG. 15 is an illustration of an exemplary multifunction magneticallyactuated photonic crystal sensor according to an embodiment of thedisclosure.

FIG. 16 is an illustration of an exemplary flow chart showing a processfor providing a magnetically actuated photonic crystal sensor accordingto an embodiment of the disclosure.

FIG. 17 is an illustration of an exemplary flow chart showing a processfor using a magnetically actuated photonic crystal sensor systemaccording to an embodiment of the disclosure.

DETAILED DESCRIPTION

The following detailed description is exemplary in nature and is notintended to limit the disclosure or the application and uses of theembodiments of the disclosure. Descriptions of specific devices,techniques, and applications are provided only as examples.Modifications to the examples described herein will be readily apparentto those of ordinary skill in the art, and the general principlesdefined herein may be applied to other examples and applications withoutdeparting from the spirit and scope of the disclosure. Furthermore,there is no intention to be bound by any expressed or implied theorypresented in the preceding field, background, summary or the followingdetailed description. The present disclosure should be accorded scopeconsistent with the claims, and not limited to the examples describedand shown herein.

Embodiments of the disclosure may be described herein in terms offunctional and/or logical block components and various processing steps.It should be appreciated that such block components may be realized byany number of hardware, software, and/or firmware components configuredto perform the specified functions. For the sake of brevity,conventional techniques and components related to manufacturing, opticalsensing, magnetic sensing, and other functional aspects of the systems(and the individual operating components of the systems) may not bedescribed in detail herein. In addition, those skilled in the art willappreciate that embodiments of the present disclosure may be practicedin conjunction with a variety of structural bodies, and that theembodiments described herein are merely example embodiments of thedisclosure.

Embodiments of the disclosure are described herein in the context of apractical non-limiting application, namely, accelerometers and sensingan open or closed state of a door such as an aircraft door. Embodimentsof the disclosure, however, are not limited to such aircraft door andaccelerometer applications, and the techniques described herein may alsobe utilized in other sensor applications. For example, embodiments maybe applicable to light switches, lock latches, collision controldevices, position of aircraft control surfaces, position of landinggear, power line voltage, power line current, and the like.

As would be apparent to one of ordinary skill in the art after readingthis description, the following are examples and embodiments of thedisclosure and are not limited to operating in accordance with theseexamples. Other embodiments may be utilized and structural changes maybe made without departing from the scope of the exemplary embodiments ofthe present disclosure.

FIG. 1 is an illustration of an exemplary magnetically actuated photoniccrystal sensor system 100 (system 100) according to an embodiment of thedisclosure. The system 100 uses magnetic fields to apply forces to amagnetic material without requiring any physical contact thereon. Themagnetic material in turn actuates a photonic crystal that is sensed bya laser. The system 100 may comprise a magnetically actuated photoniccrystal sensor 102 and a target 110.

The magnetically actuated photonic crystal sensor 102 comprises amagnetic material 104, a photonic crystal 106, and an optical fiber 108.

The magnetic material 104 is configured to sense, for example butwithout limitation, presence, absence, motion, acceleration ordisplacement of the target 110. The magnetic material 104 may compriseany of various types of magnetic material, for example but withoutlimitation, Ferrous, Ceramic, Alnico, Samarium Cobalt, Neodymium IronBoron, mixtures thereof, and the like.

The photonic crystal 106 is configured to be sensitive to forces and ismechanically coupled to the magnetic material 104. The photonic crystal106 is also coupled to a first end 112 of the optical fiber 108. Thephotonic crystal 106 is formed from, for example but without limitation,a silicon crystal base as explained in more detail below. Photoniccrystals are periodic optical nanostructures that are designed to affecta motion of photons in a similar manner to how periodicity of asemiconductor crystal affects a motion of electrons. In this manner, aperiodic optical nanostructure of the photonic crystal 106 may comprise,for example but without limitation, a lattice of optical holes, alattice of optical beads, and the like. Photonic crystals compriseperiodic dielectric or metallo-dielectric nanostructures that affect apropagation of electromagnetic waves. The propagation of theelectromagnetic waves is affected in a similar manner to a periodicpotential in a semiconductor crystal affecting an electron motion bydefining allowed and forbidden electronic energy bands. Photoniccrystals may contain regularly repeating internal regions or periodicstructures of high and low dielectric constant. The periodic structuresof photonic crystals may be used to provide optical propertiescomprising, for example but without limitation, inhibition ofspontaneous emission, high-reflectivity omni-directional mirrors,low-loss-waveguides, and the like. In this manner, the photonic crystal106 reflects a sensing light at a respective frequency.

Photons of light behaving as waves may propagate through the periodicstructures depending on their wavelength. Wavelengths of light that areallowed to travel in a photonic crystal are known as allowed modes,groups of allowed modes are known as bands, and disallowed bands ofwavelengths are known as photonic band gaps. To provide the opticalproperties mentioned above, the periodicity of the periodic structuresof the photonic crystals should be substantially of a same length-scaleas half the wavelength of the electromagnetic waves. In particular, therepeating regions of high and low dielectric constant of the periodicstructure should be substantially of an order of a half the wavelengthof the electromagnetic waves. For example, the repeating regions of highand low dielectric constants of the periodic structure should beapproximately 200 nm (blue) to approximately 350 nm (red) for photoniccrystals operating in a visible part of the electromagnetic spectrum.

The optical fiber 108 is configured to carry light to and from thephotonic crystal 106. The optical fiber 108 is protected from moisture,deformation, and the like, by a fiber coating 208 (FIG. 2). At least onelight source 116 such as at least one coherent light source 116 iscoupled to a second end 114 of the optical fiber 108 to send a coherentlight beam through the optical fiber 108 to the photonic crystal 106.The at least one light source 116, is not limited to a coherent lightsource, and may comprise, for example but without limitation, asemi-coherent light source, a non-coherent light source, and the like.The at least one light source 116, and the at least one coherent lightsource 116 are used interchangeably herein. Additionally, at least onelight detector 118 is coupled to the second end 114 of the optical fiber108 to receive reflected light from the photonic crystal 106. Light isretained in the core of the optical fiber 108 by internal reflection,causing the optical fiber 108 to act as a waveguide. Fibers that supportmany propagation paths or transverse modes are called multi-mode fibers,while those that can only support a single mode are called single-modefibers. Multi-mode fibers generally have a larger core diameter (e.g.,≧50 μm) than a core of a single-mode fiber, and are generally used forshort-distance communication links and applications where high power maybe transmitted. The larger core diameter of the multi-mode optical fibermay allow lower precision and lower cost transmitters and detectors tobe used as well as lower cost connectors. However, a multi-mode fibermay introduce modal dispersion, which may limit a bandwidth and lengthof a link. Furthermore, because of its higher dopant content, multi-modefibers generally exhibit higher attenuation than single mode fiber.Single-mode fibers are generally used for communication links longerthan about 550 meters. A core of a single-mode fiber is generallysmaller (e.g., <10 μm) than a core of a multi-mode fiber and may allowlonger and higher-performance links than a multi-mode fiber.

The target 110 (magnetically detectable object 110) is configured to besensed by the magnetic material 104. The target 110 may comprise, forexample but without limitation, an object whose motion is to be sensed,a tag placed on an object whose motion is to be sensed, a doorstructure, and the like. The target 110 may comprise, for example butwithout limitation, a magnetic material, a ferrous material, an inducedmagnetic material (e.g., induced magnetism in aluminum), a diamagneticmaterial, and the like. To improve detection, the target 110 maycomprise a multi-element target, for example but without limitation, aferrous center with a magnetic outer ring, a “strip” with alternatingmagnetic fields, and the like. With the ferrous center with the magneticouter ring, a high deflection of the magnetic material 104 may occur asthe sensor nears the magnetic outer ring, with a sudden attraction as ofthe magnetic material 104 reaches the ferrous center. With the stripwith alternating magnetic fields, the magnetic material 104 wouldoscillate as it moves over the strip.

If the target 110 is a magnetic target, depending on a pole arrangementof the magnetic target, a force in a desired direction can be induced onthe photonic crystal 106 in response to motion of the target 110. Aforce induced on the photonic crystal 106 causes optical changes in thesystem 100. If the target 110 is a ferrous target, an attraction of themagnetic material 104 to the ferrous target can cause the photoniccrystal 106 to induce an optical change such as a multi-wavelengthinterferometric change. In this manner, a motion of the target 110 canbe sensed and measured accordingly. For example, if the target 110comprises a cargo door, then closure of the cargo door may be sensed bymotion induced in the photonic crystal 106.

For cargo doors, current technology requires an inductive coil for acurrent sensor and a piece of steel (e.g., a coupon with bolt holes) asa target on the cargo door. The cargo door is usually aluminum andtherefore the current sensor only interacts with that coupon. Current isdriven through the inductive coil and a change is detected as the targetmoves into range. For the target 110 instead of the inductive coil, arelatively small magnetically actuated photonic crystal sensor such asthe sensor 102 can be used. As a ferrous or magnetic target moves inrange, it causes deflections of the magnetic material 104 and thus thephotonic crystal 106.

FIG. 2 is an illustration of an exemplary magnetically actuated photoniccrystal sensor 200 (i.e., 102 in FIG. 1 without the magnetic material104) showing a photonic crystal 202 installed on a first end 112/206 ofan optical fiber 108/206 coated by a fiber coating 208 according to anembodiment of the disclosure.

FIG. 3 is an illustration of an exemplary silicon crystal base accordingto an embodiment of the disclosure. The silicon crystal base 300 maycomprise any dielectric material, such as but without limitation, anoptical quality silicon having, a “transparency” wave length of about1.3 μm to 1.6 μm (e.g., silicon, doped silicon), and the like. Dopingmay be used to determine optical qualities of the silicon. Othermaterials, such as but without limitation, gallium arsenide, indiumgallium phosphide, copper indium gallium (di) selenide (CIGS), siliconcarbide, diamond, silicon oxide, and the like, may be also be used.

FIG. 4 is an illustration of an exemplary photonic crystal lattice 400formed by the silicon crystal base 300 comprising a plurality of etchedholes according to an embodiment of the disclosure. Etching is used tocreate the holes 402 in a material. Spacing and size of the holes 402creates the photonic crystal lattice 400. Diameters of the holes 402 maybe, for example but without limitation, about 0.25 μm to about 1.0 μm.

FIG. 5 is an illustration of an exemplary photonic crystal 500comprising a plurality of etched holes 402 separated from a substrate(not shown) to form a photonic crystal lattice such as the photoniccrystal 106/202 according to an embodiment of the disclosure. Asubstantially large amount of etching at a bottom 502 of the holes 402substantially removes the base material from which the photonic crystal106/202 is formed, thereby allowing the photonic crystal 500 to beseparated from the base material and used as the photonic crystal106/202 in the magnetically actuated photonic crystal system 100.

FIG. 6 is an illustration of a perspective bottom view 600 of thephotonic crystal 500 according to an embodiment of the disclosure. Thebottom view 600 illustrates how etching can be used to separate thephotonic crystal 106/202 from the base material from which the photoniccrystal 106/202 is formed.

FIG. 7 is an illustration of an exemplary multi-layer Fabry-Perot(etalon) Interferometer 700 formed from two photonic crystals 702 and704 (500 in FIG. 5) according to an embodiment of the disclosure. In theembodiment shown in FIG. 7, the photonic crystals 702 and 704 are placedsubstantially parallel to each other. Thickness 706 of each of thephotonic crystals 702 and 704 may be, for example but withoutlimitation, about 400 μm to about 500 μm, and the like. The photoniccrystals 702 and 704 may be separated by, for example but withoutlimitation, about 1.0 μm, and the like. In this manner, substantiallyminor changes in any one of the photonic crystals 702 and 704 can createinterference patterns needed for sensing applications. An amount oflight reflection depends on the separation distance 708. The photoniccrystals 702 and 704 form the multi-layer Fabry-Perot (etalon)Interferometer 700.

Interferometers generally use light or another form of electromagneticwave for Interferometry. Interferometry is a technique for determiningproperties of two or more waves by measuring an interference patterncreated by a superposition of the two or more waves. Interferometrymakes use of a principle of superposition to combine separate wavestogether to cause a result of the combination to have a property thatmay be used to measure an original state of the two or more waves. Whentwo waves with a substantially equal frequency combine, a resultinginterference pattern may be determined by a phase difference between thetwo waves (i.e., in phase waves constructively interfere andout-of-phase waves destructively interfere). Interference fringesbetween two coherent beams can be used to determine a motion of thephotonic crystals 702 and 704, and thereby measure a motion of themagnetic material 104 caused by the target 110.

In optics, a Fabry-Pérot interferometer or etalon is typically made of atransparent plate with two reflecting surfaces such as the photoniccrystals 702 and 704, or two parallel highly reflecting mirrors. Theformer is an etalon and the latter is an interferometer, but theterminology may be used interchangeably. A transmission spectrum as afunction of wavelength exhibits peaks of large transmissioncorresponding to resonances of the etalon.

A varying transmission function of an etalon is caused by interferencebetween the multiple reflections of light between the two reflectingsurfaces such as the photonic crystals 702 and 704. Constructiveinterference occurs if the transmitted beams are in phase, whichcorresponds to a high-transmission peak of the etalon. If thetransmitted beams are out-of-phase, destructive interference occurs,which corresponds to a transmission minimum.

For example, a single incoming beam of coherent light can be split intotwo beams by a grating or a partial mirror. Each of the two beams travela different route (path) until recombined before arriving at a detector.A path difference in a distance traveled by each beam can create a phasedifference between the two beams. The phase difference creates aninterference pattern between waves of the two beams. If a single beamhas been split along two paths then a phase difference can be used tomeasure any parameter that changes the phase along the two paths. Forexample but without limitation, a physical change in a path length, achange in a refractive index along one or more of the two paths, and thelike. The changes provide means for measuring a motion of the magneticmaterial 104.

For another example, in homodyne detection, interference occurs betweentwo beams at a substantially same wavelength. A phase difference betweenthe two beams results in a change in an intensity of the light on thedetector. Changes in the intensity can be used for measuring a motion ofthe photonic crystals 702 and 704 and thus measure a motion of themagnetic material 104.

For another example, in heterodyne detection, one of two beams ismodulated (e.g., by a frequency shift) prior to detection. In opticalheterodyne detection, an interference of the two beams can be detectedas a beat frequency. The modulated beam may comprise a signal oscillatedbetween minimum and maximum levels for every cycle of the beatfrequency. Since a modulation of the modulated beam is known, a relativephase of a measured beat frequency can be measured substantiallyprecisely even if an intensity level of each of the two beams isdrifting. Changes in the relative phase can be used for measuring amotion of the photonic crystals 702 and 704 and thus measure a motion ofthe magnetic material 104.

By measuring a motion of the photonic crystals 702 and 704, a motion ofthe target 110 is sensed via the magnetic material 104. Measurement ofthe motion of the photonic crystals 702 and 704, allows determination ofthe motion of the target 110. For example but without limitation,velocity, displacement, deceleration, acceleration and the like of thephotonic crystals 702 and 704, may be used to determine the motion ofthe target 110.

FIG. 8 is an illustration of an exemplary multi-layer Fabry-Perot(etalon) Interferometer 800 coupled to a Micro-Electro-Mechanical System(MEMS) frame according to an embodiment of the disclosure. FIG. 8 showsa representation of how a sensor using the multi-layer Fabry-Perot(etalon) Interferometer 800 might be formed in a traditional etchingprocess. Magnetic particles can be introduced into such a constructionin order to allow the sensor to sense presence or absence of a targetmaterial (magnetic or ferrous/permeable). In the embodiment shown inFIG. 8, application of the target material to the multi-layerFabry-Perot (etalon) Interferometer 800 allows detection of the presenceor the absence of the target martial. Additionally, it may be possiblefor the sensor to act as an accelerometer in some cases depending onconstruction, creating a multi-functional sensor.

FIG. 9 is an illustration of an exemplary multifunction photonic crystalsensor 900 according to an embodiment of the disclosure. Themultifunction photonic crystal sensor 900 comprises a multifunctionphotonic crystal 902 mounted on the optical fiber 206 coated by thefiber coating 208. The multifunction photonic crystal 902 comprises 2and 3-dimensional structures that may be used with 2 or 3 magnets (notshown) to detect forces in 2 and 3-dimensions respectively. In order tomeasure each function of the multifunction photonic crystal 902, a laserlight comprising two or more frequencies are used to interrogate themultifunction photonic crystal 902. Each of the two or more frequenciesmeasure one of the functions of the multifunction photonic crystal 902,and two or more light detectors (not shown) are used to receive the twoor more frequencies. The optical fiber 206 may comprise, for example butwithout limitation, a single-mode fiber, a multimode fiber, and thelike, operable to transmit the two or more frequencies. Themultifunction photonic crystal 902 may be used for, for example butwithout limitation, accelerometers, torque meters, and the like.

FIG. 10 is an illustration of a photonic crystal work-piece result 1000of a patterning step, a directional etching step, a first oxide-etchingstep, and a release-etching step in a process for forming amultifunction magnetically actuated photonic crystal sensor 1500 (FIG.15) according to an embodiment of the disclosure.

In the patterning step, a pattern mask 1002 is formed on a silicon base1004. The pattern mask 1002 comprises a lattice pattern (not shown) forforming a lattice of holes 1006. The lattice of holes 1006 may comprise,for example but without limitation, a rectangular lattice, a hexagonallattice, and the like. The lattice of holes 1006 may comprise, forexample but without limitation, cylindrical holes, spheroidal holes, andthe like. The lattice of holes 1006 may be formed by, for example butwithout limitation, directional etching, anisotropic etching, laserablation, and the like.

In the directional etching step, the lattice of holes 1006 is coveredwith an open bottom sidewall mask 1104, and the lattice of holes 1006 isfilled with an optical silicon material to form spherical holes 1102.The optical silicon material may comprise, for example but withoutlimitation, polysilicon, and the like.

In the first oxide-etching step, the pattern mask 1002 (FIG. 11), theopen bottom sidewall mask 1104 (FIG. 11), are removed via, for examplebut without limitation, oxide etching, a solvent based removal process,and the like.

In the release-etching step, excess base material 1304 is removed by,for example but without limitation, oxide etching, a solvent basedremoval process, abrasion, and the like.

FIG. 11 is an illustration of a photonic crystal work-piece result 1100of an oxide deposition step and a polysilicon deposition step in aprocess for forming a multifunction magnetically actuated photoniccrystal sensor 1500 according to an embodiment of the disclosure.

In the oxide deposition step, a silicon dioxide, or a similar film isdeposited or grown conformally on substantially all silicon surfaces.The deposited oxide is removed from horizontal surfaces by directionaletching.

In the polysilicon deposition step, polysilicon or a similar material isdeposited conformally on the photonic crystal work-piece result 1000,and then etched or polished back until the polysilicon fills the latticeof holes 1006, but does not cover a front surface (not shown).

FIG. 12 is an illustration of a second oxide-etching step 1200 in aprocess for forming a multifunction magnetically actuated photoniccrystal sensor 1500 according to an embodiment of the disclosure. Themasking layer and the oxide separating the polysilicon from thesubstrate are removed in an isotropic etch.

FIG. 13 is an illustration of a result 1300 of a silicon-etching step, abackside silicon-etching step, and a magnet-mounting step in a processfor forming a multifunction magnetically actuated photonic crystalsensor 1500 according to an embodiment of the disclosure.

In the silicon-etching step, the silicon is etched from the front (notshown) to form the desired mechanical structures that allow themultifunction photonic crystal 1302 to move in response to magneticforces and to allow release of the magnetically actuated photoniccrystal sensor 1500 before mounting on the optical fiber 206.

In the backside silicon-etching step, the silicon substrate is etchedfrom the back 1306 of the silicon base 1004 to partially release themagnetically actuated photonic crystal sensor 1500 from the substrate.

In the magnet-mounting step, the magnetic material 104 is mounted on themultifunction photonic crystal 1302.

FIG. 14 is an illustration of a fiber-mounting step 1400 in a processfor forming the multifunction magnetically actuated photonic crystalsensor 1500 according to an embodiment of the disclosure. The magneticmaterial 104 and the multifunction photonic crystal 1302 are mounted onthe optical fiber 206.

FIG. 15 is an illustration of an exemplary multifunction magneticallyactuated photonic crystal sensor 1500 according to an embodiment of thedisclosure. The multifunction magnetically actuated photonic crystalsensor 1500 is operable to be sensitive to two or more measurands, wherea measurands is a particular quantity subject to measurement. Themultifunction magnetically actuated photonic crystal sensor 1500 isinterrogated by many wavelengths (e.g., λ₁, λ₂, λ3, . . . ) as thesewavelengths are measurands. The reflectivities on the fiber 206 at thedifferent wavelengths (i.e., λ₁, λ₂, λ₃, . . . ) depend differently onthe measurands, so the measured reflectivities at a chosen wavelength(R₁, R₂, R₃, . . . ) allows calculation of the measurands (S₁, S₂, S₃, .. . ). For example, for multiaxis magnetic field sensing, two measurandsS₁ and S₂ may measure the motion in direction X and direction Zrespectively.

FIG. 16 is an illustration of an exemplary flow chart showing a processfor providing the magnetically actuated photonic crystal sensor 102according to an embodiment of the disclosure. The various tasksperformed in connection with process 1600 may be performed mechanically,by software, hardware, firmware, or any combination thereof. Forillustrative purposes, the following description of process 1600 mayrefer to elements mentioned above in connection with FIGS. 1-15. Inpractical embodiments, portions of the process 1600 may be performed bydifferent elements of the magnetically actuated photonic crystal sensor102 such as the magnetic material 104, the photonic crystal 106, theoptical fiber 108, the at least one coherent light source 116, and theat least one light detector 118. Process 1600 may have functions,material, and structures that are similar to the embodiments shown inFIGS. 1-15. Therefore common features, functions, and elements may notbe redundantly described here.

Process 1600 may begin by providing a photonic crystal 106/202 (task1602).

Process 1600 may then continue by coupling the photonic crystal 106/202to the first end 112/206 of the optical fiber 108/204 (task 1604).

Process 1600 may then continue by coupling a magnetic material 104 tothe photonic crystal 106/202 (task 1606).

Process 1600 may then continue by coupling the at least one light source116 to the second end 114 of the optical fiber 108/204 (task 1608). Inthis manner, the optical fiber 108/204 transmits light waves from the atleast one light source 116 to the photonic crystal 106/202.

Process 1600 may then continue by coupling the at least one lightdetector 118 to the second end 114 of the optical fiber 108/204 (task1610). In this manner, the optical fiber 108/204 transmits light wavesfrom the photonic crystal 106/202 to the at least one light detector118, which detects the light waves.

Process 1600 may then continue by sensing a magnetically detectableobject 110 (task 1612), such as but without limitation, an aircraftdoor, a train door, an automobile door, a house door, a gate, a vault,and the like.

Process 1600 may then continue by determining whether the magneticallydetectable object 110 (e.g., a door) is closed (task 1614). For example,the magnetically actuated photonic crystal sensor 102 senses forcechanges due to presence or absence of a door in a proximity thereof anddetermines whether the door is closed or not based on a predeterminedmeasurement. When the door is closed, the proximity of the magneticmaterial paced on the door substantially changes the forces on themagnetically actuated photonic crystal sensor 102/1500. This in turnchanges a reflectivity at a monitoring wavelength, so that a measuredreflectivity less than a chosen threshold shows that the door is open,and a measured reflectivity greater than a chosen threshold shows thatthe door is closed. In an alternative embodiment, a measuredreflectivity less than a chosen threshold shows that the door is closed,and a measured reflectivity greater than a chosen threshold shows thatthe door is open.

FIG. 17 is an illustration of an exemplary flow chart showing a processfor using the magnetically actuated photonic crystal sensor system 100according to an embodiment of the disclosure. The various tasksperformed in connection with process 1700 may be performed mechanically,by software, hardware, firmware, or any combination thereof. Forillustrative purposes, the following description of process 1700 mayrefer to elements mentioned above in connection with FIGS. 1-15. Inpractical embodiments, portions of the process 1700 may be performed bydifferent elements of the magnetically actuated photonic crystal sensorsystem 100 such as the magnetic material 104, the photonic crystal 106,the optical fiber 108, the at least one coherent light source 116, theat least one light detector 118, and the magnetically detectable object110. Process 1700 may have functions, material, and structures that aresimilar to the embodiments shown in FIGS. 1-15. Therefore commonfeatures, functions, and elements may not be redundantly described here.

Process 1700 may begin by receiving a received magnetic force on amagnetic material coupled to the photonic crystal 106 such that thephotonic crystal is actuated by the received magnetic force (task 1702).The magnetic force may be received from the magnetically detectableobject 110.

Process 1700 may then continue by transmitting a transmitted lightthrough the optical fiber 108 to the photonic crystal 106 (task 1704).

Process 1700 may then continue by receiving a reflected light throughthe optical fiber 108 from the photonic crystal 106 (task 1706). Asexplained above, the photonic crystal 106 may modify the reflected lightbased on the received magnetic force, for example but withoutlimitation, based on interferometry, and the like, in the photoniccrystal 106.

Process 1700 may then continue by determining a determined difference inthe reflected light from the transmitted light (task 1708). Thedetermined difference may be obtained, for example but withoutlimitation, based on interferometry of the reflected light and thetransmitted light, and the like.

Process 1700 may then continue by detecting at least one property of themagnetically detectable object based on the determined difference (task1710). As explained above, the at least one property may comprise, forexample but without limitation, speed, acceleration, deceleration,vibration, displacement, immobility and the like. For example, thedisplacement may be measured based on a measured reflectivity. In thismanner, measured reflectivity less than a chosen displacement thresholdmay indicate a door is open (or closed), and a measured reflectivitygreater than the chosen displacement threshold may indicate that thedoor is closed (or open).

Process 1700 may then continue by operating the magnetically actuatedphotonic crystal sensor system in an environment (task 1712). Theenvironment may comprise, for example but without limitation,contamination, obscurants, obstructions, debris, potential sources ofphysical deformation, and a non-contaminated environment.

In this way, various embodiments of the disclosure provide a method forproviding a magnetically actuated photonic crystal sensor. Embodimentsprovide means for sensing force changes on a magnetic material thatactuate a photonic crystal without any physical contact thereon. Becausemagnetic actuation requires no physical contact, the magneticallyactuated photonic crystal sensor system is operable in an environmentcomprising obscurants, obstructions, debris, and/or potential sources ofphysical deformation as well as in contamination free environments.

While at least one example embodiment has been presented in theforegoing detailed description, it should be appreciated that a vastnumber of variations exist. It should also be appreciated that theexample embodiment or embodiments described herein are not intended tolimit the scope, applicability, or configuration of the subject matterin any way. Rather, the foregoing detailed description will providethose skilled in the art with a convenient road map for implementing thedescribed embodiment or embodiments. It should be understood thatvarious changes can be made in the function and arrangement of elementswithout departing from the scope defined by the claims, which includesknown equivalents and foreseeable equivalents at the time of filing thispatent application.

The above description refers to elements or nodes or features being“connected” or “coupled” together. As used herein, unless expresslystated otherwise, “connected” means that one element/node/feature isdirectly joined to (or directly communicates with) anotherelement/node/feature, and not necessarily mechanically. Likewise, unlessexpressly stated otherwise, “coupled” means that oneelement/node/feature is directly or indirectly joined to (or directly orindirectly communicates with) another element/node/feature, and notnecessarily mechanically. Thus, although FIGS. 1-15 depict examplearrangements of elements, additional intervening elements, devices,features, or components may be present in an embodiment of thedisclosure.

Terms and phrases used in this document, and variations thereof, unlessotherwise expressly stated, should be construed as open ended as opposedto limiting. As examples of the foregoing: the term “including” shouldbe read as mean “including, without limitation” or the like; the term“example” is used to provide exemplary instances of the item indiscussion, not an exhaustive or limiting list thereof; and adjectivessuch as “conventional,” “traditional,” “normal,” “standard,” “known” andterms of similar meaning should not be construed as limiting the itemdescribed to a given time period or to an item available as of a giventime, but instead should be read to encompass conventional, traditional,normal, or standard technologies that may be available or known now orat any time in the future. Likewise, a group of items linked with theconjunction “and” should not be read as requiring that each and everyone of those items be present in the grouping, but rather should be readas “and/or” unless expressly stated otherwise. Similarly, a group ofitems linked with the conjunction “or” should not be read as requiringmutual exclusivity among that group, but rather should also be read as“and/or” unless expressly stated otherwise. Furthermore, although items,elements or components of the disclosure may be described or claimed inthe singular, the plural is contemplated to be within the scope thereofunless limitation to the singular is explicitly stated. The presence ofbroadening words and phrases such as “one or more,” “at least,” “but notlimited to” or other like phrases in some instances shall not be read tomean that the narrower case is intended or required in instances wheresuch broadening phrases may be absent.

The invention claimed is:
 1. A magnetically actuated photonic crystalsensor, comprising: an optical fiber comprising a first end; at leastone photonic crystal means coupled to the first end; and at least onemagnetic material coupled to the at least one photonic crystal.
 2. Themagnetically actuated photonic crystal sensor of claim 1, wherein theoptical fiber comprises a single-mode fiber, a multimode fiber, anoptical waveguide, or a combination thereof.
 3. The magneticallyactuated photonic crystal sensor of claim 1, wherein the at least onephotonic crystal means comprises a lattice comprising optical holes,optical beads, or a combination thereof.
 4. The magnetically actuatedphotonic crystal sensor of claim 1, wherein the at least one photoniccrystal means is operable to reflect a sensing light at a respectivefrequency.
 5. The magnetically actuated photonic crystal sensor of claim1, wherein the at least one photonic crystal means is operable tomeasure motion in a respective direction.
 6. The magnetically actuatedphotonic crystal sensor of claim 1, wherein the at least one photoniccrystal means is operable to measure displacement in a respectivedirection.
 7. The magnetically actuated photonic crystal sensor of claim1, wherein the at least one photonic crystal means comprises a periodicdielectric nanostructure, a metallo-dielectric nanostructure, silicon,gallium arsenide, indium gallium phosphide, copper indium gallium(di)selenide (CIGS), silicon carbide, diamond, silicon oxide, or acombination thereof.
 8. A magnetically actuated photonic crystal sensorsystem, the system comprising: a magnetically detectable object; anoptical fiber comprising a first end; at least one photonic crystalcoupled to the first end; and at least one magnetic materialmechanically coupled to the at least one photonic crystal, andconfigured to receive a magnetic force from the magnetically detectableobject such that the at least one photonic crystal is actuated by themagnetic force; at least one light source configured to transmit atransmitted light through the optical fiber to the at least one photoniccrystal; and at least one light detector configured to receive areflected light through the optical fiber from the at least one photoniccrystal.
 9. The system of claim 8, wherein at least one property of themagnetically detectable object is detected based on a determineddifference in the reflected light from the transmitted light.
 10. Thesystem of claim 9, wherein the at least one property comprises speed,acceleration, deceleration, vibration, displacement, immobility, or acombination thereof.
 11. The system of claim 8, wherein the magneticallydetectable object is not in physical contact with the at least onemagnetic material.
 12. The system of claim 8, wherein the at least onemagnetic material is mounted on the at least one photonic crystal. 13.The system of claim 8, wherein the at least one magnetic material iscoupled to a side of the at least one photonic crystal.
 14. A method forproviding a magnetically actuated photonic crystal sensor, the methodcomprising: providing a photonic crystal; coupling the photonic crystalto a first end of an optical fiber; and coupling a magnetic material tothe photonic crystal.
 15. The method of claim 14, further comprisingcoupling at least one light source to a second end of the optical fiber.16. The method of claim 15, further comprising coupling at least onelight detector to the second end of the optical fiber.
 17. The method ofclaim 14, further comprising sensing a magnetically detectable object.18. The method of claim 17, further comprising determining whether themagnetically detectable object is closed, wherein the magneticallydetectable object is a door.
 19. The method of claim 17, wherein themagnetically detectable object comprises a magnetic material, a ferrousmaterial, an induced magnetic material, a diamagnetic material, or acombination thereof.
 20. The method of claim 14, wherein providing thephotonic crystal further comprises: patterning the photonic crystal;etching holes in the photonic crystal; and releasing the photoniccrystal from a substrate.